It has previously been proposed to monitor tire pressure by a transducer within each vehicle tire. Several schemes have been tried for advising the vehicle operator of tire pressure conditions, especially in the case of low tire pressure. It is known, for example, to generate a visible signal at the tire and to visually inspect the signal. It is also known to generate a magnetic field at the transducer in response to a low pressure condition, to detect the field by a detector mounted near each wheel, and to display a warning on the instrument panel. It has also been proposed to mount a transducer and radio transmitter within each tire and a receiver on the vehicle dedicated to processing transmitted tire pressure data and displaying necessary information.
One known system using tire-mounted transmitters and a receiver has the feature of displaying which of the four tires has low pressure. Four transmitter identification numbers (IDs), each dedicated to a tire position, are supplied for all vehicles so that the manufacturer must supply four different part numbers to service the four IDs and a customer would have to order replacement according to wheel position. With this system a receiver may pick up a valid ID from a neighboring vehicle, thereby obtaining false information, and tire rotation would cause confusion in the displayed information.
It has also been proposed in a transmitter-receiver system to have only one transmitter part number with each transmitter having a unique ID. On this system it is required to have a learning method to marry four sender IDs to a particular receiver. One way of doing this is by approaching each tire with a magnet close to each sender location to trigger a transmission that would be captured by the receiver. At this point the receiver needs to be placed in a learn mode to be able to program each sender ID in permanent memory. A predetermined order of wheel positions needs to be followed to program the senders for specific display positions. This arrangement requires human intervention as well as a programming tool for teaching the tire sender IDs.